Identification of a novel 10.3 kb deletion causing α-thalassemia by third-generation sequencing: Pedigree analysis and genetic diagnosis.

Background: α-thalassemia is an inherited blood disorder caused by variants in the α-globin gene cluster. Identification of the pathogenic α-globin gene variants is important for the diagnosis and management of thalassemia.

Methods: Two suspected families from Xiantao, Hubei Province were recruited in this study. The family members underwent hemoglobin testing. Polymerase Chain Reaction based reverse dot blot (PCR-RDB) was employed to identify the known variants. Next-generation sequencing (NGS) and third-generation sequencing (TGS) were performed to screen the potential disease-causing variants, which were validated by Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA).

Results: Hematological analysis suggested that proband A had α-thalassemia traits, and proband B had HbH disease traits. However, only a -α mutation had been detected by PCR-RDB and NGS in the proband of family B. Subsequent TGS identified a novel 10.3 kb deletion (NC_000016.10:g.172342-182690del) covering the HBA1, HBQ1 and HBA2 genes in the α-globin gene cluster in both family A and B, which was confirmed by Sanger sequencing and MLPA. These results indicated that the novel deletion is likely responsible for α-thalassemia.

Conclusion: A novel α-thalassemia deletion was identified for the two families by TGS. Our work broadened the molecular spectrum of α-thalassemia, and was beneficial for the diagnosis, genetic counseling and management of α-thalassemia.